Brain surgery is an effective treatment for many individuals who suffer from medically intractable epilepsy. Functional brain mapping techniques have the potential to improve the outcome of this treatment by identifying patients at particular risk of cognitive morbidity, by identifying vital brain tissue that should not be removed at surgery, and by helping to identify abnormal, epileptogenic brain tissue that should be removed. There remain, however, many unresolved issues regarding these applications. There are as yet no generally accepted protocols for localization of language or memory systems, the two cognitive domains at greatest risk from epilepsy surgery. It is not clear which mapping protocols, if any, reliably identify vital tissue in the anterior temporal lobe or anterior hippocampus, where the majority of epilepsy resections are performed. No studies have yet provided evidence that functional brain mapping helps to minimize cognitive decline or improve seizure control. This proposal is for continuation of an ongoing project to develop standardized and reliable functional magnetic resonance imaging (fMRi) methods for these purposes. The overall goal is to minimize language and memory decline from epilepsy surgery, which depends on precise presurgical localization of the critical components of these processing systems. To achieve this goal, we will (1) assess two fMRI language mapping protocols and two medial temporal lobe activation protocols for predicting language and verbal memory decline after anterior temporal Iobectomy, the most common form of epilepsy surgery; (2) assess the ability of these fMRI protocols to identify the side of seizure origin in patients with temporal lobe epilepsy; and (3) compare the predictive power of fMRI with that of current standard tests, such as the Wada test, neuropsychological testing, and interictal positron emission tomography. These studies will constitute the first large-scale and rigorous assessments of the clinical validity and utility of presurgical functional brain mapping in epilepsy. Their successful completion will lay a firm foundation for use of these techniques to improve the outcome of epilepsy surgery.